1. Field of the Invention
The present invention relates to a defibrillator/cardioverter of the type having a plurality of n (n.gtoreq.3) electrodes which are connected to a device for generating electric pulses.
2. Description of the Prior Art
A defibrillator or cardioverter is disclosed in German OS 3,919,498, wherein one of a plurality of electrodes is arranged in the interior of the heart and the remaining electrodes are placed outside of the heart. The external electrodes are electrically connected to one another and are connected to a first of two output terminals of a pulse generator. The electrode arranged in the interior of the heart is connected to the second output terminal. It is thereby achieved that, upon the transmission of an electrical pulse by the pulse generator, the electrical current density is distributed in the heart muscle in accordance with the arrangement of the electrodes and preferably penetrates the thickest zones of the heart muscle, which form the main part of the heart muscle mass, in order to achieve defibrillation or cardioversion. The current distribution, however, can be set only by the arrangement and size of the individual electrodes. The arrangement of the electrodes, and in particular their distance from one another, is limited, however, by the anatomical conditions.
U.S. Pat. No. 4,548,203 discloses a further defibrillator having a plurality of electrodes which are connected in pairs to different outputs of a pulse generator and are placed on different, preferably opposite, sites of the heart. In order to defibrillate the heart, one electric pulse is applied to the individual electrode pairs sequentially via the outputs of the pulse generator, the pulses being separated from one another in each case by a time interval. The spatially and temporally separate pulse transmission is intended to achieve a reduction in the energy required to trigger the defibrillation. In each case, however, only two electrodes simultaneously participate in the pulse transmission, and thus a genuine distribution of the current density to different zones of the heart muscle is difficult to achieve if at all.
In a further defibrillator, disclosed in U.S. Pat. No. 4,708,145, having three electrodes, transmission of defibrillation pulses is performed sequentially between a first electrode and in each case one of the other two electrodes, the pulses again being separated from one another by a time interval.
European Application No. 92104392.3 (corresponding to pending U.S. application Ser. No. 07/856,688, filed Mar. 24, 1992, Hirschberg et al., "Defibrillator/Cardioverter"), discloses an arrangement which achieves a spatially optimum current distribution when the individual electrodes are connected to respective output terminals, which are in turn connected to a plurality of series-connected outputs of a pulse generator which simultaneously transmits an electric pulse at each of those outputs.